Ultra high frequency device



E. G. LWL-3ER 292959678 ULTRA HIGH FREQUENCY DEVICE Filed June 25, 19,40

f I A jrwenfor Patented Sept, iSd-2';

n gesamt l rarest. ortica v v y 'giilanornavia I Ernest G.

` 1Linder, Philadelphimla.; assgnor to r lltadio Corporation of America,- a corporation of Delaware applicationrane 25, 1940, semaines/2,235 geminis.` (chest-s6) rI'his invention relates to ultra. 'high frequency radio devices, and more particularly to animproved shielding system for microwave radio'appay ratus. It has for its principal object 'the provision of an improved microwave signal generator.

rlhe use of signal generators in aligning, testing and measuring radio Vreceivers and other radio apparatus is well known. For the measurement of sensitivity, for example, the receiver is coupled to the generator and the output voi the' generator reduced by an attenuator until the receiver output is equal ,to some predetermined standard value. 1I'he amplitude of the signal generator output may be reduced to several microvolts where the receiver sensitivity is fairly high.'

it is, of course, necessary for the generator out put terminals to be the sole source of energy Afor the receiver ii the measurement is to have any meaning. Unfortunately, however, this is' not easily accomplished, since a certainamount of leakage is usually found, particularly at high` frequencies. For this reason, signal generators are always carefully shielded. HoWeveL shielding which is satisfactory in the low and evenV in moderately high frequency ranges is entirely inadeouate in ultra high frequency or microwave ranges. f

l' have discovered that theY principal cause of leakage is the relatively poor Contact between the main portion of the container and removable portions, such as doors and partitions, which of necessity cannot be welded or soldered into place. For example, tube replacements must sometimes be made, and it is Atherefore customary to provide one or more removable sections which are normally retained in place by thumb or machine screws. Phosphor bronze springs bearing on the surface of the removable section are of some help, but they do not solve the problem. The result is that it has heretofore been extremely dilcult to keep the leakage radiation down to a proper level. Another source of trouble is the leakage which occurs through meters and controls which are mounted in the iront panel of the generator.

in accordance withthepresent invention, this radiation or leakage is minimizedby providing enti-resonant cavities or compartments-in which i the energy leaking through the removable sections of the shield is tuned out. Alternatively,

the shielding' container itselfis made'to have such a size that it is non-resonantl at the desired operating frequency.

Additional objects of this invention include the provision of an improved method of and means and around'the various vide laccess tothe apparatus.

for preventing radiation loss-from a source of ultra highA frequency energy; the provision of an improved system for preventing radiation through and around instruments mounted in the panel of a 'radio device; the provision of an improved attenuator vfor a signal generator, and the provision of an improved capacitor arrangement for in'- suring adequate bypassing on conductors which may have standing waves along their length.

ThisV invention will be better understod from the following description when considered in connection with` the accompanying drawing, and its scope is indicated by the appended claims.

Referring to the drawing,

Figure 1 is a simpliiied drawing of a shielding system in accordance with the present invention; and

Figure 2 is a view, partly in cross-section, of an ultra high frequency generator embodying this invention.

'Similar reference v numerals refer to similar parts throughout the several figures of the drawing.

' Fig; l illustrates a high frequency energy source 3, which is an oscillator, amplifier or any other radio apparatus which requires shielding to prevent radiation or to protect it from high irequency energy in the surrounding area. This Vdevice is mounted in a shielding container 5 which is, for example, a metallic box closed on five sides by solidly welded or soldered sections, or constructed in one piece, through which no leakage can occur. The sixth side 'l is removable to pro- The removable side 1 may be 'a hinged door or a removable plate held in place by screws, or any otherconstruction which is expedient. As pointed out above, however, even when the abutting surfaces are clean and tight some leakage will occur, and this increases from day to day as the contacting surfaces of the metal oxidize. To minimize this leakage radiation, a second removable shielding member 9 is provided, which forms a cavity i0 adjacent the'iir'st removable section 7.' rihe invenior is aware, of course, thatit is not new to "provide merely two-shields in the place'of one. `What is new, however, is the discovery that radia- The purpose of this arrangement is to make certain that the leads are grounded at a point which is not a voltage node. Since the leads are effectively grounded through a length equal to a quarter wave, some point within the block will necessarily be that corresponding to a voltage loop, and hence the grounding will be effective. This arrangement is particularly advantageous where the device is operated over a wide range of frequencies, since the bypassing will be uniform and equally effective notwithstanding changes in the standing waye distribution along the lines.

The invention thus involves an improved antiresonant shielding system for ultra high frequency radio devices, and is not restricted to the particular embodiment thereof. It is to be understood that many different embodiments of this invention will occur tc-those skilled in the art. This invention, therefore, is to be limited only by the prior art and the spirit of the appended claims. Claims specific to elements shown and described but not covered by the appended claims will be found in my copending application, Serial No. 400,488, led June 30, 1941, for Indicators.

I claim as my invention:

1. In a radio device, a shielding container enclosing a source of ultra high frequency oscillations, a removable partition dividing said container into separate compartments, one of said compartments containing said source, the size of the other of said compartments being adjusted to a condition of anti-resonance at the frequency of said oscillations whereby the electric field strength in said other compartment due to leakage around said removable partition is minimized.

2. A shielding container for preventing undesired radiations from a source of ultra high frequency oscillations, said container having a removable inner wall to provide access to the interior of said container, and an outer wall adjustably spaced from said inner wall, the distance between said walls being such that at said ultra high frequency an antiresonantl condition is 1 produced and the electric field intensity therebetween is minimized.

3. An ultra high frequency oscillation generator including a source of ultra high frequency oscillations, a shielding container enclosing said source and having a removable portion to pro- Vide access to the interior of said container, an adjustable shielding member spaced from said removable portion and forming a closed anti-resonant compartment at the operating frequency of said generator, whereby leakage radiation around said removable portion is minimized.

4. An ultra high frequency generator including a source of ultra high frequency oscillations, a shielding container for said source having a removable end portion, leakage around said end portion causing undesired radiations from said and generator, and an adjustable shielding compartment enclosing said end portion, said compartment being adjusted to a condition of antiresonance at the operating frequency to minimize standing waves in said shielding compartment.

5. An ultra high frequency generator including a source of ultra high frequency oscillations, a shielding container having a removable end portion, leakage around said end portion causing undesired radiation i rom said ing compartment enclosing said end portion, and means for slidably adjusting one dimension of said compartment to form an anti-resonant cavity at said operating frequency to minimize standing Waves therein and minimize said undesired radiation.

6. In an ultra high frequency generator, a sourceL of oscillations, a shielding container for said source, said container having a removable end portion, a shielding compartment enclosing said end portion, means for adjusting said compartment to produce an anti-resonant condition therein at the operating frequency of said source, and means for deriving output currents from said source.

'7. In a radio device, the combination comprising a. shielding container, an ultra high fre-l quency radio device Within said container, said container having a removable wall portion to provide access within said container, an adjustable member constructed to slide telescopically over said shielding container so as to enclose said removable portion and form therewith an antiresonant compartment at the operating frequency of said device whereby leakage around said removable portion is minimized.

8. An ultra high frequency radio device which includes the combination of a source of ultra high frequency oscillations, a shielding container for said source, said container having a removable end portion, and means adjustably mounted on said container for forming With saidv end portion an antiresonant compartment at the operating frequency of said device whereby leakage around said removable portion is minimized.

9. An ultra high frequency radio device which includes, in combination, a source of ultra high frequency oscillations, a shielding container for said source, a section of said container being removable to give access to said container, means mounted on said container forming a closed compartment with said section, and means for slidably adjusting the position of said last-named means to tune said compartment to a condition of antiresonance at the operating frequency of said device, whereby standing Waves in said compartment due to leakage around said section are minimized and leakage radiation from said container is also reduced.

ERNEST G. LINDER.

generator, a shicld- 

